Influence of Stoichiometry on the Optical and Electrical Properties of Chemical Vapor Deposition Derived MoS₂

الأصل · EN

Ultrathin transition metal dichalcogenides (TMDCs) of Mo and W show great potential for digital electronics and optoelectronic applications. Whereas early studies were limited to mechanically exfoliated flakes, the large-area synthesis of 2D TMDCs has now been realized by chemical vapor deposition (CVD) based on a sulfurization reaction. Since then, the optoelectronic properties of CVD grown monolayer MoS₂ have been heavily investigated, but the influence of stoichiometry on the electrical and optical properties has been largely overlooked. Here we systematically vary the stoichiometry of monolayer MoS₂ during CVD via controlled sulfurization and investigate the associated changes in photoluminescence and electrical properties. X-ray photoelectron spectroscopy is employed to measure relative variations in stoichiometry and the persistence of MoOₓ species. As MoS₂₋δ is reduced (increasing δ), the field-effect mobility of monolayer transistors increases while the photoluminescence yield becomes non-uniform. Devices fabricated from monolayers with the lowest sulfur content have negligible hysteresis and a threshold voltage of 0 V. We conclude that the electrical and optical properties of monolayer MoS₂ crystals can be tuned via stoichiometry engineering to meet the requirements of various applications.